Process for recovering metallic tin and antimony-tin alloy from sb-snas bearing materials



Feb'. 17, 1948. Y. E. LEBEDEFF 2,436,010

PROCESS FORXRECOVERING METALLIC TIN AND ANTIMONY-TIN ALLOY FROM SB-SN-AS BEARING MATERIALS Filed nec. 24, 1945 v kfw/wv To mareas INVENTOR' BY nmz' L? mdf/y @am f. W

ATTORNEY i KETTLE AEf//v//v FEF/NED T/N Patented Feb. 17, 1948 UNITED s'rAT ES QiFF'l-CE.,

rRooEss Fon REcovEmNGAMETALLIo 'rm AND ANTIMONY-'rm ALLOY mioM sii-SN: As BEARING MATERIALS l Yurii E. Lebeaeff, Manchen, it J., `assigner fio American Smeltng New York, N. Y.; met

Application December24, 1943;` Serial No.l 515,;178l 4 Claims. (Cl. Maf-1go) K This invention relates to a process of recovering antimony and tin and more particularly to the electrowinningof antimony-tin alloy and tin from antimony-tin-arsenic bearing materials.

The recovery of tin from varioustin-bearing. materials has received considerable attention, in View of the high value of tin as a strategic metal, and many proposals have been made for expediting the recovery of tin fromthe various tin-bearingV materials thatl are available. Generally speaking, however, all the proposedv processes of the priorart are open to certaink objections, among which, primarily, are the rather incomfv pleterecoveries of'tin which are effected by such processes and/ or the costs involved in the variousV operations whereinthe tin recoveries` are rela-r tively high.

The present invention differs fundamentally from kthese prior proposals in that tin recoveriesr arehigh, costsare relatively low, and substantial` ly pure metal is obtained, witnthe ultimate fre-V covery of practically all of the values contained in the starting material. Further,l the presentv process provides `a continuous cyclic process forA the recovery of these values, together with elli?k cient Vrecoveries of reagents fory re-use in the 'prociess.`

According ,to the invention there is provideda continuous process for the krecovery of"tinvand1 other values contained in complex tin-bearingv materials,l such as complex sulphide ores, concern--` trates, orfoxilicmaterials'wherein the tin is 'prese ent tin oxide, the process involvingthe. confv version of the tin into a water-soluble form, whereby it may be separated from associatedma` terials such as lead,l copper, bismuth, precious metals, and thev like. In' order to accomplishv this solubilizingV operation, they tin content 'of' the starting materials is convertedlinto vv,atuer..`` soluble tin compounds, which may be extractedV by leaching with water from insoluble sulphicesr which, contain elements suhfas lead, 101021812 iron; bismuth and any other componentspresent which( may form Water insoluble sulphide's, together with precious metals. s

The tin is recovered from the resumingV leached solution, which is high in tin,.and may beA obi jectionably high in arsenic and antimony, byel cftrolysis,` preferentially as yto antimony in order toV strip the antimony from the solution, while leave ing the. bulk of theftin and arsenicv inthe elecj trolyte, the eli'ectrolyss being carried out initially until the antimony conte'nthas been lowered," to; 3`vgrainsper liter o'r less. Thel electrolyte is then s lrtl1i-ary electrolyzeV to. deposit the tin, l"along with any, remaining; antimonv! Af Small amount of arsenicimar also: be ,.deiiositrY.v This deposited' metal. is th. after rened injacszorderm s With Standard prg. eauresio profiu puremeillic tiri! Thei'elsidual 4,electrolyfte may be' evaporatedfsuf# ciently ktoadepositj k the issolvedffsalts therefrom, which reliever@ `Salismay be returned f t0' 'the process. as reagents?, The delimited im; which contains nie antiwar is preferably Subicte, to, `stan.,ClarY, kettle-refiere,Ddures ioslolie reacting tfwth sodium sulphide, ,A alkli ysulphide, which 'may' be; A produced, ini situ in, .tlef furnace fbytheI reducing actionl ofcarbo ons'odiu'm si'ilphata'orby the' addition, of .sodium uipnide'v itse1f to the "charge, or,liybthe;featitj r`f1-l pf, sulphur 'on the charge, f'oll lou/,ed by a fusion. offftheresultingH material with,

2Q causticalkali'.i Erorn econonliclc'onsid'erations,"it` is'preferred't'o operatebymiiiin'g'th charge withfy sodiunjiv sulphateA or 'bi'sulphate' Yand carbon," care' bei'nsst" In: that" there,isgsumoientavanabie soif.

presentin thefreaction 'mixture'tof sulwi 'sulphurffIf the"'requisitefsulphurris nota reypr'esentin 4nace"wli'cli maybe heatejdeith'er. byffrl'rl by electricity, the"furnace preferably' 35, hel` l '.theheartn untilitv melts, theiesulting molten'rnatte beingfallowedfto Vflow continuouslyl 4.0, i s Y timefinfthe furnace',"are carefully controlled so' that i'lpl'alzilizationV of` tin' yin any appreciable an'i'o'unts[is"aifoic'iedA As a' furthersafeguard against loss of jtin, it is preferable in,l practice',v

when using areve'vr'beratory typ furnaceto pro-l vide, a vsuitable baghouse orf otherfumelcollect'- iingegiiipment to collect the evolved'fume, which isQreturn'ed to the melting furnace. Operatingl with'an electric furnace, however,4 where the heat 50 no. tin fume is"pr0 enmi'nated;

As thernolten matte runs into the pool of Wa tent esnlting,solutionispunripeol throughany one, of @number @differences of arsenite duififihe beghouss may b u pin izeujfcomponents orithemateriai that willA the charge', it may beadded g material is fed 'continuouslyinto ch' dissolves the' sodium; sfulpho onipounds of tinjantimony' and arsenic4 produced." by thesulphidizing treatment. rThe' condi onsof melting, such as' vtemperatures and` treatment can be zcci'iratelyy controlled so that"V cycled into the tank containing thepool of water employed for granulation and solution of soluble constituents. 1y contains less than 1% tin.

The clarified concentrated thio-solution from the thickening or settling step lcontains* from 50 to 80 grams per liter of tin together with the antimony and arsenic present in the original material. This concentrated thin-'solution containthe tin-bearing material is then electrolyzed using insoluble anodes which are madev of material resistant to corrosive attack by the alkali polysulde solution, such'as a 14.5% silicon cast iron or similar high silicon-iron alloy. The solution is electrolyzed to preferentially deposit out the antimony. Ordinary steel sheet may be used as .the cathode during deposition of antimony inasmuch as antimony 'deposited thereon is easily removed by scraping or the like mechanical treatment. The ysolution is electrolyzed at ordinary room temperature using cathode'current densities of from about 20 to 36 'amperes per square foot and voltage of approximately 4. Antimony present in the concentrated thio-#solution is depletedto controlled amounts. Preferably, this initial electrolysis is carried out until there remains not more than about 3.0 grams per liter of antimony'in the electrolyte. This value, of course, may vary somewhat depending upon the original concentration ratioy of antimony, tin and arsenic and the degree of purity of tin desired to be recovered. v

After substantially all of the antimony has been deposited from the polysulphide electrolyte solution the cathodes are removed and replaced by substantially antimony-free electrodes. Preferably tin sheet is utilized as the cathode material and the electrolysis is continued to recover f the tin as described below. The initial electroly'l sis removes substantially all the antimony along with a relatively small percentage amount of tin, A the resulting antimony-tin cathode deposit being removed and either melted into a marketable alloy, or refined to recoverthe values therefrom.

The solution remainingfrom the antimony lelectrolysis step, which is rich in tin and which contains preferably not 4more than 3 grams perY of approximately 4, similarly as in electrowinning Athe antimcny. The resulting tin deposit which contains small amounts of antimony, the amount depending upon the tin to antimonyV ratio in the electrolyte solution at the termination Aof the an-V timony stripping operation. The antimony content in the tin is ordinarily in the neighborhood of 4%, with traces of arsenic. This tin product may be kettle refined in accordance with standard procedures to produce a more highly rened The process effects a-rapid; and economical,

fas well as relatively clean separatioiiof antirnony,A tin and arsenic,l Vwhen present,"from materials' The dried cake material usuale containing the same, and results in a highly eiii=1 cient tin recovery process, which is substantially continuous. The cyclic character of the process also affords an economic reuse of reagents, thereby reducing substantially the amounts of fresh reagents that are required to be employed in the process.

Of course an important consideration in the successful operation of the process depends upon an eifective conversion of the tin in the original Y.material into water-soluble form as an alkali sulpho-stannate. It is found that this conver- .sion .isaccomplished effectively by the present process fora 'widely different kind of complex if the startingV material contains no appreciable amounts of arsenic and antimony, the recovery ing substantially all the tin originally present in A.

of. the-tin is simplified by the omission of the antimon'y-lremoving steps of the process and the rening of the metallic tin produced. y The invention may be better understood by reference to the accompanying drawing constituting a diagrammatic flow sheet of the process.

As speciiicexamples of the process the following are given as typical.

EXAMPLE 1Y A chargewas prepared comprising a tin-sulphide flotation concentrate and sodium sulphate and coke as reducer, the charge being prepared in the ratio of 5.0 parts by Weight of sodium sulphate and 30 parts by weight of coke for each 100 parts by weight of concentrate. In view of the fact that this concentrate was already a sulphide material, no additional sulphur is needed to be added. The concentrate assayed as follows: S 35%, Sn 10%, Cu 15%, Pb 5%, Ag 500 0z./t., Au trace, Fe 28%, Sb 2.5%, As 0.5%, Bi 0.5%, SiOa 1.5%, CaO 0.5%, A1203 0.5%Zn 1%. The resulting charge rvvas fed continuously into a furnace of a reverberatory type malntained at a temperature of about 1800* F., and provided with a'sloping hearth so that the molten matte resulting from diffusion will ovv continuously from the furnace. The furnace was red by oil-burners directed in the direction of travel of the charge in the furnace, the atmosphere of the furnace being maintained neutrai or on the reducing side.

Where not enough sulphur is present in the charge it is necessary to introduce sufilcient sulphur in the charge to react with all sulphideforming components of the original material. Sufficient alkali metal must be added to react with all the tin, antimony and arsenic present to convert them into alkali thio-sulphides, which are water-soluble, and to operate the `furnace with a controlled atmosphere which is maintained reducing in its action while avoiding temperatures and time of contact of the materials in discharge from the furnace being controlled so as `to minimize tin losses by fuming. In practice,

however, it is desirable to provide some type of fume-collecting equipment, so that evolved fume maybe collected and returned to the furnace.

The pool of water serves to granulate the matte.

'Invthe melting reaction, the tin, arsenic, and-'- fio ntlmony, have been rendered water-soluble through conversion into their corresnalldtig-..

sodium-sulpho-salts. Water removed from the granulating pool is replenished at the same rateiA the solution is withdrawn, so that a. solution of.. substantially constant concentration is handled.

The resulting solution as it is formedi may be passed through any standard type thickeningV i*4 settling equipment, which is found .to lbeivery'- suitable for the treatment of this solution.V Even )Q n a lter press may be employed if it has suiflcient Y capacity to handle the volume of solution beingtreated. l y

After removing the insoluble mattenithefltrate containing the tin, antimony and. arsenic in the form of water soluble sulphur compounds was subjected to electrolysis to recover thatantimony and tin as described. -1- p EXAMPLE 2 Leached press cake produced from the sul- ;phuric acid-leaching O f oxidized ffwhite matte. assay'ing Sn 33.2%, S 3.25%, Pb 16.0%;,Gli10.5.%,

' f lNi.- 2.4%;Fe. 8.8 --Zn;2-.0 ,g SiOz19..6 Sb: L8 As- 0.3%.-Wasrtreated bythisgprocess. Since this. `inmaterial is esser1t,1'l a1.1y:v a. sulphated- Kexidic -material.; for efficient operation.-it is 4necessary-to ,-111.- tlo duce' additinal.:sulphur-,td the Ghalge in; order to effect.complete-sulphidizingof ,the component-s \.of...the matenlal. Theficharge-was prepared'arby mixing .ther-reagents' irr.Y the proportions of ,100

imballi-'191'. yllaji Tin Antimony v I n 'r paths K emp. 'Y Amp. Grams Total Grams Tomi 0. A??? vd'fs HIS. I per Y gli Kg. met xg. sq. fz.n

..... 31.0 49.6 v 9.3 14.581 f 1s. 24.57 30.3 43.6 3.0 4.7ir '26' 30.2 3.74

Electrolysis temporarily suspended while Vcathodes are moved and 'replaced with antimony-freecathodes for receiving the tin deposit:Y

33.44 26.5 42.4 0.3 .48 40 37.43 26.1 40.16 4 0.2` 32 40 61.46 21.2 V33.92 0.0` 0.0V 26 102. 02 13. 1 20. 96 0. 0 l 0.0 30

133. 26 9.3 14.788 0.0 0.0 28 165. 66 v5. 7 9. l2 0.0 0. 0 30 204.06 3.7 5.92 0.01 f0.0., 32 213.06 3.42r Y 5. 12 0.0 f 0.0 31

once-zenuw From the above tables it will be seen that my process provides a relatively simple and efficient method of recovering'metallic tin in a-fairly pure state from alkali-thio-stannate solutions containing large amounts of antimony and arsenic sulpho-oompounds as additional constituents in solution.A Further, while the invention has been Vdescribed as particularly applicable to the selective removal of antimony and.v tinl from alkali-` thio-solutions containing antimony, tin and arsenic, it will be understood that my process may be employed for treating various kinds of complex tin-bearing materials' containing antimony or arsenic to recover metallic tin and antimony or alloys thereof.l

This application is a continuation-impart oi' Vmony and arsenic wherein the tin-bearing matemy prior application Serial No. 358,999, led

September 30, 1940, now abandoned.

While certain novel stepsof my new process -have been specicallydisclosed and are pointed.-

out in the annexed claims, itwill be understood that various omissions, substitutions and changes may be made by those skilled nthe art Without departing from the spirit and scopeof my.

invention. t

What is claimed is:

the tinhas been deposited leaving the arsenic in solutionL-fv f N v2. In the artA of producing substantially pure tin from tin-bearing material containing antirial is` smelted with material supplying alkali lmetal sulphide to convert the tin, antimony and arsenic into Water-soluble sulphides whichA are dissolved in water forming a solution of consid- .erably greater tinv content than of antimony and arsenic and from which tin is electrolyzed and subsequently further reiined by melting and drossing the melt to produce substantially pure tin, the method of recovering the tin from said solution substantially free from antimony, arsenic and other impurities which consists in electrolyzing said solution having an antimony content of more than three grams per liter at room temperature using insoluble anodes and a cathode current density of from 20 to 36 amperes per square foot and voltage of approximately 4 to preferentially strip the antimony therefrom in the form of an alloy of antimony l. In the art of recovering tin from tin-bearing material containing antimony and arsenic tration of more than three `grams p er liter, at

room temperature using insoluble anodes and a cathode current density of between 20 to 36 amperes per square foot and voltage of approximately 4, to preferentially strip the electrolyte' solution of antimony in the formV of an alloy containing a relatively small smount of tin until the antimony content of the'solu'tion'has been lowered to about three grams or less per liter l concentration, thereafter, and Awithout materially` Y varying its chemical composition or concentration, subjecting the antimony depleted solutionA which is rich in tin to further electrolysis: at room temperature using insoluble anodes and substantially antimony-free cathodes to depositY the tin preferentially of the arsenic, and discontinuing the electrolysis when substantially all of and tin until the antimony content of the solu- `tion is lowered to approximately three grams per liter or less, and then subjecting the antimony vdepleted solution which contains most of the original tin and arsenic to further electrolysis at room temperature using insoluble anodes and `substantially antimony-free cathodes and employing a current density of from 18 to 32 amperes per square foot and voltage of approximately 4 to deposit out the tin preferentially from the electrolyte leaving the arsenic in solution.

3. A continuous process of treating ores containing tin, lead, copper, antimony, bismuth, arsenic and precious metals to recover tin which comprises the steps of smelting the ore with alkali, sulphur and carbon reagents to convert the tin, arsenic and antimony into a Water-soluble sulphide matte, introducing the matte while molten into a pool of Water to cause distintegration of the matte and form a solution of the metal sulphides in which the concentration of substantially all the antimony therefrom, and subjecting the antimony depleted electrolyte containing tin and arsenic to further electrolysis using a current density of between 18 to 32 amperes per square foot and voltage of approximately 4 to remove the tin while leaving the arsenic in solution.

4. The process for recovering relatively pure tin from complex tin-bearing ores, concentrates, and other tin-bearing metallurgical materials wherein tin is associated with heavy metals, which comprises continuously introducing into a smelting furnace a mixture of the said materials with reducible alkali compounds and reducing agent therefor, smelting the said mixture in the presence of sufiicient sulphur to and arsenic and the antimony exceeds three grams per liter, separating antimonyfrom the said tin-bearing solution by electrolyzing the solution at room temperature preferentially with respect to the antimony using insoluble anodes and a cathode current density of between 20 and 10 36 amperes per square foot and voltage of a proximately 4 thereby depositing substantially major amounts of the antimony while retaining at least the major portion of the tin in the electrolyte solution, removing the cathodes on which the antimony has been deposited and replacing them with substantially antimony-free cathodes, and further electrolyzing the said solution at room temperature and using a cathode current density of between 18 and 32 amperes per square foot with a voltage of about 4 until substantially lall the tin has been deposited on said antimonyfree cathodes.

YURII E. LEBEDEFF. REFERENCES CITED The following references are of record in the le of this patent:

FOREIGN PATENTS Number Country y Date 13,641 Great Britain 1896 294,703 Great Britain Aug. 2, 1928 OTHER REFERENCES Electrolytic Methods of Analysis, Neumann, published 1898 by Whittaker & Co., New York, pp. 201-204, inclusive.

Zeitschrift fur Elektrochemie, vol. 4 (1897-98), pp. 244 to 247.

' Practical Methods of Electro-Chemistry, by F. M. Perkins, published by Longmans, Green & Co., New York, 1905, pp. 181, 182, 183. 

